Loans and Allowance for Loan Losses - Recorded Investment in Loans Modified in TDRs (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	$ 455,000	$ 6,496,000	$ 13,457,000	$ 7,153,000
Loans classified as TDRs, charge-offs	0	1,200,000	0	1,200,000
Commercial loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	455,000	6,496,000	13,457,000	7,083,000
Consumer loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0	0	0	70,000
Software
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	455,000	778,000	12,816,000	778,000
Hardware
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0	5,629,000	0	5,629,000
Venture capital/private equity
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0	89,000	0	676,000
Premium wine
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0	0	641,000	0
Consumer loans
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period	0	0	0	70,000
Payment Deferrals Granted
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period		6,500,000	10,800,000	7,200,000
Forgiveness Of Principal
Financing Receivable, Modifications [Line Items]
Loans modified in TDRs during the period			$ 2,700,000